1. Field of the Invention
The invention relates to epoxide resin mixtures which harden at room temperature and are comprised of epoxide resins (EP resins) based on bisphenol A, aliphatic or cycloaliphatic polyamines with more than 2 H atoms in the molecule, and polyether polyol/diisocyanate prepolymers wherein the free NCO groups are blocked with selected piperidine derivatives.
2. Discussion of the Background
EP resins hardened with polyamines are distinguished in practice by a number of desirable properties, e.g., good adhesion to all possible substrates, good solvent resistance, and high resistance to the action of chemicals. Due to the high crosslinking density of the amine-hardened EP resins, particularly such resins based on bisphenol A, these resins are brittle, with glass transition temperatures above 20.degree. C., and therefore means must be taken to make them flexible, particularly in the case of applications for which impact strength, shock resistance, and high flexibility are required.
The compounds most often used to plasticize cold-hardened amine/EP resin compounds are the aromatic carbamic acid aryl esters described in Ger. OS 21 52 606. These esters are bound into the polymer network upon hardening of the EP resins and polyamines, such binding occurring due to the reaction of the amino groups with the carbamic acid ester groups whereby alkylphenol is liberated.
A crucial drawback of amine-hardened EP resins plasticized with carbamic acid esters is the fact that they harden only slowly at room temperature (RT), because the amino groups react substantially slower at RT with the carbamic acid ester groups than with the EP groups. Despite the good mechanical properties of plasticized epoxy resins, no one has yet developed a plasticized amine-hardened EP resin which rapidly hardens at room temperature.